Meeting Abstract

S4.9  Monday, Jan. 5  Phylogeny and evolution of eusocial insects: a comparison of origins and losses in ants and bees BRADY, S.G.*; DANFORTH, B.N.; CARDINAL, S.; Smithsonian Institution; Cornell University; Cornell University bradys@si.edu

We review recent progress toward understanding the evolutionary history of eusocial insect societies, which are characterized by cooperative brood care, generation overlap, and reproductive division of labor. Eusociality has evolved in several insect groups, most prominently in ants, bees, wasps, and termites. Ants and bees both originated approximately at the same time in the Cretaceous (approximately 120-140 million years ago) yet these two taxa contrast notably in their manifestations of eusociality. In ants, eusociality evolved only once and has never been lost. Ant groups have evolved specialized versions of eusociality that incorporate highly complex morphological caste systems and behavioral innovations such as pack hunting and fungal agriculture. The vast majority of bee species are solitary, and eusociality has evolved 5-6 separate times in bees alone. The highly eusocial honey bee, focus of much current developmental and genomic research, thus represents only one of several distinct eusocial bee lineages. Eusociality in halictid bees evolved much more recently compared to other major eusocial insect groups, with three independent origins approximately 20-25 million years ago. These bees display substantial diversity and flexibility in their expression of eusociality and show frequent reversals back to solitary condition. These characteristics may allow halictid bees to provide a more direct window into the origins and early development of social insect societies.